Inhibition of Tulane virus replication in vitro with RNA interference

Abiotic Stress and Phyllosphere Bacteria Influence the Survival of Human Norovirus and Its Surrogates on Preharvest Leafy Greens

Foodborne outbreaks of human noroviruses (HuNoVs) are frequently associated with leafy greens. Because there is no effective method to eliminate HuNoV from postharvest leafy greens, understanding virus survival under preharvest conditions is crucial. The objective of this study was to evaluate the survival of HuNoV and its surrogate viruses, murine norovirus (MNV), porcine sapovirus (SaV), and Tulane virus (TV), on preharvest lettuce and spinach that were subjected to abiotic stress (physical damage, heat, or flood). We also examined the bacteria culturable from the phyllosphere in response to abiotic stress and in relation to viral persistence. Mature plants were subjected to stressors 2 days prior to inoculation of the viruses on leaves. We quantified the viral RNA, determined the infectivity of the surrogates, and performed bacterial counts on postinoculation days (PIDs) 0, 1, 7, and 14. For both plant types, time exerted significant effects on HuNoV, MNV, SaV, and TV RNA titers, with greater effects being seen for the surrogates. Infectious surrogate viruses were undetectable on PID 14. Only physical damage on PID 14 significantly enhanced HuNoV RNA persistence on lettuce, while the three stressors differentially enhanced the persistence of MNV and TV RNA. Bacterial counts were significantly affected by time and plant type but not by the stressors. However, bacterial counts correlated significantly with HuNoV RNA titers on spinach and with the presence of surrogate viruses on both plant types under various conditions. In conclusion, abiotic stressors and phyllosphere bacterial density may differentially influence the survival of HuNoV and its surrogates on lettuce and spinach, emphasizing the need for the use of preventive measures at the preharvest stage.

In vitro inhibition of field isolates of feline calicivirus with short interfering RNAs (siRNAs)

Feline calicivirus (FCV) is a common infection of domestic cats. Most infections are mild and self-limiting; however more severe disease manifestations, such as FCV-associated virulent systemic disease, may be associated with significant morbidity and mortality. There is currently a lack of effective antiviral treatments for these disease manifestations. In this study, a panel of eight siRNAs were designed to target four conserved regions of the FCV genome. siRNAs were screened for in vitro antiviral efficacy against the reference strain FCV F9 by determination of extracellular virus titres and morphological assessment of protection from cytopathic effect. Three of the siRNA (FCV3.7, FCV4.1, and FCV4.2) demonstrated a marked antiviral effect with a greater than 99% reduction in extracellular viral titre. Titration of these effective siRNAs demonstrated a clear concentration-response relationship, with IC50 values of approximately 1 nM, and combination treatment with multiple siRNAs demonstrated additive or synergistic effects. To assess the potential usefulness of the compounds in a clinical setting, siRNAs were screened against a panel of six recent Australian FCV isolates from cats with FCV-related disease. The siRNAs shown to be effective against the reference strain FCV F9 were active against the majority of the isolates tested, although some variability was noted. Taken together these data suggest potential therapeutic application of antiviral RNAi for treating FCV-associated disease in cats.